ABSTRACT ? Recruitment and Assessment Core The overall goal of the Duke Autism Center of Excellence is to characterize how co-occurring symptoms of attention deficit hyperactivity disorder (ADHD) influence the early detection, clinical presentation, brain mechanisms, developmental trajectories, and treatment outcomes of young children with autism spectrum disorder (ASD). Across Projects 1, 2, and 3, investigators will evaluate young children with ASD alone, ASD with co-occurring ADHD, ADHD alone, and typically-developing children. The Recruitment and Assessment Core will provide centralized services in recruitment and assessment of participants across projects, thereby ensuring that the overall Center accomplishes its recruitment goals, obtains high quality participant data, and is positioned to achieve project-specific aims and conduct novel cross-project analyses. The Core has the following aims: (1) recruit, screen, and enroll participants for Duke ACE Center projects by collaborating closely with the Dissemination and Outreach Core and by engaging in a variety of recruitment strategies such as advertising, community event participation, and maintaining active relationships with local advocacy and support groups; (2) provide standardized, reliable assessment of participants by administering common core assessments, including ASD and ADHD diagnostic measures, and collecting other cognitive, behavioral, family and medical history, intervention history, and environmental exposure data to characterize all Center participants. By overseeing the fidelity and inter-rater reliability of centralized common measures, assessment quality will be increased; (3) implement strategies to maximize retention of participants by promoting a positive experience for participants and their families. Strategies will include maintaining regular contact with participants, providing diagnostic reports that summarize testing results, responding promptly to queries, and giving regular updates about Center research and activities. As part of its role in retaining participants, Core staff will collaborate with the Data Management and Analysis Core to help manage and implement the Cohort Management System developed for Project 1; and (4) track recruitment and retention and address barriers to successful recruitment and retention. Core staff will establish goals and milestones related to recruitment and retention that correspond to the needs of each project and provide weekly updates to the Administrative Core and Executive Committee regarding progress. Staff will monitor and proactively address barriers to meeting goals, thereby ensuring that all projects will be successful in achieving their research aims. By effectively completing these aims, the Recruitment and Assessment Core will reduce staff burden and use resources more effectively to ensure that the Duke ACE Center will meet its recruitment and retention goals, provide high quality, standardized phenotypic characterization of all participants, and facilitate novel cross-project analyses and discoveries that integrate common data on participants.